Method for processing wire

ABSTRACT

A method for producing a heat and corrosion resistant, ironnickel chromium-alloy wire with a roughened and oxidized surface by first etching the surface of the wire with an acid mixture of nitric, hydrochloric and acetic acids and thereafter passing the wire along a flame to oxidize the surface and anneal the entire body of the wire simultaneously.

United States Patent Geissler et al.

[ Aug. 21, 1973 METHOD FOR PROCESSING WIRE Inventors: George N. Geissler, West New York;

Harry Clark Smith, Upper Montclair, both of NJ.

Assignee: Wilbur B. Driver Company, Newark,

Filed: July 16, 1971 Appl. No; 163,148

Related US. Application Data Continuation-in-part of Ser. No. 19,606, March 16, 1970, abandoned.

US. Cl. 156/18, 252/79.4 Int. Cl. C23f 1/04 Field of Search 156/18, 4; 252/794 [56] References Cited UNITED STATES PATENTS 449,861 4/1891 Pender et al 156/18 1,939,241 12/1933 Taylor 156/18 X Primary Examiner-Jacob ll. Steinberg Attorney-Norman J. OMalley, Donald R. Castle etal.

57 ABSTRACT 4 Claims, 1 Drawing Figure o o /I\\ C) O 0 0 OD alr- gas

|2 l6 22 CONSTANT QUENCH SPEED TANK LINE R'BBON $55; 20 COLE'EZISLI/ABLE WINDER BURNER HEATED ACID ETCHING TANK PAYOFF METHOD FOR PROCESSING WIRE CROSS-REFERENCE TO RELATED APPLICATION This application is a Continuation-in-Part of application Ser. No. 19,606, filed Mar. 16, 1970 and now abandoned which is assigned to the assignee of the present invention.

BACKGROUND OF THE INVENTION Certain new types of glass to metal seals require use of a wire formed from a heat and corrosion-resistant seal alloy and characterized by a rough surface having an adherent outer layer formed from one or more oxides of this alloyi Essentially, all of these alloys are iron-nickel-chromium-alloys, thus making etching and oxidizing difficult.

After experimenting unsuccessfully with a variety of techniques such as drawing the wire to size in an unpolished carbide die, sanding the wire with various abrasive materials and etching in acid, we succeeded in producing the desired type of surface by first etching the surface of the wire in a particular mixture of selected acids and thereafter passing the etched wire in a heated zone to simultaneously anneal the body of the wire and oxidize the surface thereof.

SUMMARY OF THE INVENTION In our process, heat and corrosion resistant iron-nickel-chromium-bearing glass sealing alloy wire is passed through an etching bath containing a mixture of nitric, hydrochloric and acetic acids until asmall portion of the wire is removed and a uniformly rough surface is obtained. Thereafter, the wire is passed over a hot flame until the body of the wire is annealed and an adherent oxide layer is formed on the surface.

BRIEF DESCRIPTION OF THE DRAWING The accompanying drawing illustrates our process diagrammatically.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS For a better understanding of the present invention together with other and further objects, advantages, and capabilities thereof, reference is made to the following disclosure and appended claims in connection with the above description of some of the aspects of the invention.

Generally, alloys which are sealed into glass have to be corrosion and heat resistant as well as having controlled expansion coefficient since different atmospheres are present inside and outside the device in which they are used. For example, an alloy of iron, 42 percent nickel with about 6 percent chromium is often used. The chromium is added to increase the adherence of the oxide, however, etching and oxidization are difficult. By etching the wire immediately prior to oxidizing with the etchant used in the process of this in vention, the resulting activated surface is thereafter covered readily by an adherent film of a black oxide. In general, the process can be used with any ironnickel-chromium alloy. An etched surface aids in glass sealing. The acid mixture which has been found to produce desirable results without destruction of desired properties is an aqueous mixture of nitric, hydrochloric and acetic in the percentage ranges hereinafter set forth.

The aqueous acid mixtures can consist essentially from about 3 to about 5 percent by weight of acetic acid, from about 12 to about 20 percent by weight hydrochloric, from about 30 to about 50 percent by weight nitric and balance water. The foregoing acid mixtures are suitable for etching the foregoing alloy wires which are bright annealed or hard drawn.

Referring now to the drawing, an iron, 42 percent nickel, 6 percent chromium bearing sealing alloy wire 24 is unwound from tension controllable payoff 22 and passed through a heated acid etching tank 20 to etch and toughen the wire surface. The wire then is washed by passing through a spray rinse 18. The cleaned wire surface is then passed over ribbon burner 16 to anneal the wire and oxidize the surface and then is passed through the quench tank 14 and an air wiper l2. Fi nally, the wire is coiled on a constant speed winder 10.

EXAMPLE Typically the seal alloy wire had the following composition:

Nickel 42 percent 1 Chromium 6 percent Iron 52 percent Approximately 0.0003 inch 0.0005 inch was etched away from the wire (which had an initial diameter of 0.0404 inch) as it was passed through the etching solution. The solution was composed of forty percent water, forty percent concentrated nitric acid, sixteen percent conccn trated hydrochloric acid and four percent concentrated acetic acid, all measured by volume. The nominal operating solution temperature was l45F. The etching rate can be controlled-by changing the length (normally 2 feet) of wire in solution, or by altering either the solution temperature or the processing speed (normally feet per minute) of the wire.

Following the etching process, the wire was washed by exposure to water spray rinses using unneutralized water.

The etched wire then was passed through a series of adjustable guide pulleys located before and after the line-ribbon burner. The pulleys are adjustable in three dimensions to enable proper positioning of the wire over the oxidizing flame.

The flame was adjusted to obtain a sharp, blue cone approximately three-eighths of an inch high. The air pressure was set at about fifty pounds per square inch and the city gas flow rate was adjusted for proper flame condition. The wire was positioned to travel just above the cone of the flame. When the oxidizing-annealing operation is performed properly, the wire will be heated to a yellow-orange color.

The hot wire was quenched as it passed through a meniscus of water. The meniscus was obtained by pumping water into the bottom of an upright cylinder and allowing it to overflow at the top. The water is collected and recirculated.

The air wiper was used to blow the wire dry before the wire was spooled on a constant speed, traversing spooler.

The oxide surface should be examined for adherence and color (normally a dull, dark charcoal gray). The thickness of the finished wire should be maintained between 0.0396 inch and .0404 inch in diameter.

The above process can be used for any wire formed from the class of sealing alloys having a high content of nickel and iron in addition to chromium.

While there have been shown and described what are at present considered the preferred embodiments of the invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the scope of the invention as defined by the appended claims.

What is claimed is:

l. A process for producing a corrosion and heat resistant iron-nickel-chromium glass to metal sealing alloy wire with a roughened and oxidized surface comprising the following steps:

a. etching the wire in an aqueous acid mixture consisting essentially of from about 3 to about 5 percent by weight of acetic acid, from about 12 to about 20 percent by weight of hydrochloric acid. from about 30 to about 50 percent by weight of nitric acid, balance water,

b. passing the etched wire through a heated zone to simultaneously oxidize the surface and anneal the entire body of said wire.

2. A process according to claim 1 wherein the zone includes a hot flame over which the wire is passed.

3. A process according to claim 2 further including the step of rinsing the etched wire prior to passage through the zone.

4. A process according to claim I wherein said wire is an iron 42 percent nickel 6 percent chromium alloy 

2. A process according to claim 1 wherein the zone includes a hot flame over which the wire is passed.
 3. A process according to claim 2 further including the step of rinsing the etched wire prior to passage through the zone.
 4. A process according to claim 1 wherein said wire is an iron -42 percent nickel - 6 percent chromium alloy. 